PROFESSOR V IRC HOW AND EVOLUTION. 647 
checks licentiousness in speculation while the thing to 
be repressed, both in science and out of it, is dogmatism. 
And here I arn in the hands of the meeting, willing to end 
but ready to go on. I have no right to intrude upon you 
unasked the unformed notions which are floating like clouds, 
or gathering to more solid consistency in the modern specu- 
lative mind." 
I then notice more especially the basis of the theory. 
"Those who hold the doctrine of evolution are by no 
means ignorant of the uncertainty of their data, and they 
only yield to it a provisional assent. They regard the 
nebular hypothesis as probable; and, in the utter absence 
of any proof of the illegality of the act, they prolong the 
method of nature from the present into the past. Here 
the observed uniformity of nature is their only guide. 
Having determined the elements of their curve in a world 
of observation and experiment, they prolong that curve into 
an antecedent world, and accept as probable the unbroken 
sequence of development from the nebula to the present 
time." Thus it appears that, long antecedent to the pub- 
lication of his advice, I did exactly what Professor Virchow 
recommends, showing myself as careful as he could be not 
to claim for a scientific doctrine a certainty which did not 
belong to it. 
I now pass on to the Belfast Address, and will cite at 
once from it the passage which has given rise to the most 
violent animadversion. " Believing as I do in the contin- 
uity of nature, I cannot stop abruptly where our micro- 
scopes cease to be of use. At this point the vision of the 
mind authoritatively supplements that of the eye. By an 
intellectual necessity I cross the boundary of the experi- 
mental evidence, and discern in that ' matter' which we, 
iu our ignorance of its latent powers, and notwithstanding 
our professed reverence for its Creator, have hitherto 
covered with opprobrium, the promise and potency of all 
terrestrial life." Without halting for a moment I go on 
to do the precise thing which Professor Virchow declares 
to be necessary. " If you ask me," I say, " whether there 
exists the least evidence to prove that any form of life can 
be developed out of matter independently of antecedent 
life, my reply is that evidence considered perfectly con- 
clusive by many has been adduced, and that were we to 
follow a 'common example, and accept testimony because 
